Seller Note “PC wont turn on with this card installed”
Summary
- Condition is solid enough, but well used, dust, warranty sticker broken, new thermal paste and pads fitted (a little poorly)
- I bought it for £22.98 (I am hoping for a fixable short, I like this style of card)
- Resistances
- VCore – 1.5Ω
- VMem – 50.9Ω (Samsung)
- VDDCI – 29.8Ω
- Display Rail – 24.6Ω
- 5V – 553Ω
- 1.8V – 2.6KΩ
- 3.3V – 2.1KΩ
- 12V – 0.7Ω! (slot), 2.4KΩ+ (8 pin)
Investigating the 12V rail short on the PCI input
For this type of card, having a PCI bus short seems much less common than being short on the 8 pin PCI-EXT (typically the VCore VRM, involving more power, sometimes burns), so I am hopeful for maybe a less serious short. Normally I would proceed by measuring the gate resistance of each high-side MOSFETS, but because we are seeing a dead short to ground, I am going to try injecting 0.9V instead into the PCI 12V rail and see how much current is drawn and whether anything gets warm.
Injecting 0.9V immediately draws more than 4 Amps and I can feel warmth close to the lowest phase nearest the PCI slot. The thermal camera shows the culprit (capacitor circled):
Removing this capacitor, it is indeed shorted. I don’t know it’s value, so I also removed the one above which measured 10uF. Replacing them both restores the 12V PCI rail resistance to 4KΩ+
I am pretty hopeful at this point, as 12V shorts go, this is generally a lucky case! Reassembling the card, and testing, it works well 🙂 However, to complete it, I would like to clean it and replace those rough-looking thermal pads.
exelent!
Thanks for the feedback 🙂